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ADS1262 chop mode

Herve NONON
Prodigy 150 points
Other Parts Discussed in Thread: ADS1262

Hi Everybody,

I'am using ADS1262 to scan 10 differents sensors ( 8 thermocouples with x32 gain, and 2 others with x1 gain). First tests (with default parameters FIR, 20SPS and 1.1ms delay) works fine but i need data more often. After each "data ready",i read result, then write 4 registers from MODE0 to INPMUX (Group1)

old values : 0x48,0x80,0x54,0x2A (for channel 2) : it works :)

new values : 0x58,0x60,0x5A,0x2A : it does'nt work :(                 (2400 SPS, chop mode, SINC4, 1.1ms delay)

After writing registers, i just send a START1 command (0x08) and wait for a low level on "data_ready" which never occure...

Is there anybody to help me ?

Thank you.

Hervé

  • 0
    TI__Mastermind 44680 points

    Hi Hervé,

    I did some testing on my end and I think I was able to the replicate the problem...

     

    Problem Description
    It appears like the issue only occurs when the ADS1262 is in pulse convert mode AND chop is enabled. Once in this mode, sending START1 will provide a single conversion result; however, issuing the START1 command again does not appear to start additional conversions...This leads to the behavior you're seeing, where /DRDY no longer goes low.

     

    Workaround
    I need to investigate this issue in more detail. However, I think I have a temporary solution...

    If you send the STOP1 command, then issue another START1 command you'll be able to start another conversion and /DRDY will go low again. Just add the STOP1 command somewhere in your sequence (either before or after writing to the registers), and you should see /DRDY go low again.

    UPDATE: Please refer to the following post for more details...
     

    Best Regards,
    Chris

  • 0 in reply to Christopher Hall
    Prodigy 150 points

    Thank you very much, Chris

    I will try it... and come back to say if it works...

    Regards

    Hervé

  • 0 in reply to Herve NONON
    Prodigy 150 points
    Hi Chris,
    I just made some tests with "STOP1", but those didn't works, perheaps because my fimware with a lot of interrupts. I always read 0000000 as result ( read before conversion ?). ADS1262 is just a little piece in a big project and i need to go on : i will make "chop mode" in firmware : 20 conversions for 10 sensors and adding results to calculate offset. Thanks again for help and tell me if you find better issue.
    Best Regards.
    Hervé
  • 0 in reply to Herve NONON
    TI__Mastermind 44680 points

    Hi Hervé,

    It sounds like there may be more to your SPI communication issues. It would be a good idea to monitor the SPI communication with a logic analyzer. I personally use this logic analyzer while developing and debugging software, until I've proven the correct functionality...

    If you need help debugging SPI communication, we're always willing to look at logic analyzer or o-scope screenshots of the SPI communication to help find the problem!

    Best Regards,
    Chris